PV Diagram help - Monatomic ideal gas change of state

AI Thread Summary
The discussion focuses on calculating the work done on a monatomic ideal gas during a change of state from A to D on a PV diagram, with the work calculated as 1215.6 J for the constant volume and constant pressure paths. The main challenge arises in determining the change in internal energy without knowing the number of moles or temperature. It is clarified that internal energy depends on temperature, and the user suggests using the ideal gas law to express internal energy in terms of pressure and volume. Ultimately, the user resolves the issue and expresses gratitude for the assistance received.
prj
Messages
2
Reaction score
0

Homework Statement


Suppose a monatomic ideal gas is changed from state A to state D by one of the processes shown on the PV diagram (attached). a) Find the total work done on the gas if it follows the constant volume path A-B followed by the constant pressure path B-C-D. b)Calculate the total change in internal energy of the gas during the entire process and the total heat flow into the gas.

Homework Equations



W= -P(Vf-Vi)
dU = Q + W
dU = 3/2nRT

The Attempt at a Solution


I found the answer to part A to be 1215.6 J of work were done on the gas. My problem comes in part b. How can I determine the change in internal energy without knowing the number of moles (n) of the gas, or the temperature?
 

Attachments

  • gas.png
    gas.png
    14.4 KB · Views: 996
Physics news on Phys.org
Do you really need n to calculate the change in internal energy? Remember that U depends only on temperature, so what is the temperaure difference?
 
prj said:
dU = 3/2nRT

How can I determine the change in internal energy without knowing the number of moles (n) of the gas, or the temperature?

Shouldn't that be dU = 3/2nRdT? Or ΔU = Δ(3/2nRT)? Maybe you can use the ideal gas law to write this in terms of P and V rather than nRT.
 
I think I was over-complicating the problem, but I've solved it now.

Thank you for the help!
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Calculating ΔE Difference for 2 Samples of Monatomic Ideal Gas
Replies
4
Views
2K
Why is temperature constant after gas has expanded?
Replies
33
Views
2K
PV Diagram of Ideal Monatomic Gas Processes
Replies
4
Views
2K
Internal Energy of an Ideal Gas
Replies
4
Views
2K
How Does Expansion Affect Internal Energy in a Monatomic Ideal Gas?
Replies
1
Views
2K
How do I calculate work and heat in a PV diagram for an ideal monoatomic gas?
Replies
11
Views
2K
PV diagrams monatomic ideal gas
Replies
1
Views
4K
Why Might Statement (b) Be Incorrect in Ideal Gas Processes?
Replies
2
Views
2K
Energy of a Gas in equilibrium with BB-radiation
Replies
9
Views
2K
Closed cycle of an ideal gas
Replies
3
Views
1K

Hot Threads

Recent Insights

Back
Top